I second Jon as I've been on roughly the same plan. I generally ride before breakfast if on weekday or Saturday laps. Breakfast will generally be unflavoured yoghurt with fruit or scrambled Egg with salmon/veggies. No complex carbs.
Fuelling on rides (if really long) has been fruit/nuts outside carb window, something with complex carbs inside it and then fruit/nuts on way in. No flavoured drinks or gels outside window and I use water with neutral tabs all the time.
Gradually built up endurance.
@SteveHunt49 - sorry missed this totally.
I do what I would call "semi Keto". I'm not convinced on the benefits of Keto for endurance sports, as the body needs carbs at points. What I do is limit my carb intake to the middle of the day on normal days, and about an 1.5 hrs before an intense effort (eg: VO2 max sessions on the turbo).
For me, there is little point putting complex carbs in after around 2pm. Unless you are doing a massive session, you won't burn through them in everyday life, and overnight your body will turn them into fat. So any work you did that morning to burn the fat is negated. I also don't see the point in a breakfast of complex carbs if you're only doing a aerobic exercise session in the am (commute, light weights etc).
I've been doing this two years now, and have found it a simple way of fuelling for rides and keeping my weight down.
Caveat: this works for me, and I'm not a doctor/nutritionist
For example, my daily routine might be:
Weights or turbo session
Breakfast - usually low fat yogurt with berries (black, blue, rasp, straw) and mango, coffee and yakult
Mid morning snack of fruit or nuts (if I have a banana it will be around now)
Lunch - lean meats, veg, grains, potatoes, maybe bread or pasta. Usually somewhere around 40g of complex carbs (fist full).
Post lunch snack - popcorn or pop chips or similar
afternoon snack - fruit or nuts
Dinner - lean meat/salad/veg - no complex carbs
Evening snack - nuts, seeds, maybe a little dark (75%+) chocolate
This is accompanied by 12-15k steps/day, loads of water and copious green tea
Zwift race days - if a race is circa 7:30 I will have a bowl of porridge around 5:30 with honey and berries. I will have a banana halfway through the race.
Club ride fuel: I will work on high fat nuts and seeds - macadamias are little balls of energy and on a club ride you'll burn straight through them.
Sportive fuel: Start out on slow burning carbs (peanut butter sarnies etc) and migrate to gels/gummies for that last bit of energy. Mixture of snacks like nuts and maybe a bar or two for the lull points.